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ATEL # 2722; M. Armas Padilla, R. Kaur, N. Degenaar, R. Wijnands (University of Amsterdam), F. Lewis (Faulkes Telescope Project, University of Glamorgan, Open University), D. M. Russell (University of Amsterdam).
on 4 Jul 2010; 11:08 UT
Password Certification: Rudy Wijnands (firstname.lastname@example.org)
Subjects: X-ray, Binaries, Black Holes, Neutron Stars, Transients
Referred to by ATEL #: 2738
We continued our Swift-XRT monitoring of the new very-faint X-ray source XMMSL1 J171900.4-353217 [ATel #2607, #2656]. Two new observations were obtained on Jun 14th and 29th and we fitted both observations with an absorbed powerlaw model, keeping the hydrogen column density constant to the value 3.4E22 cm-2 (see ATel #2627). The resulting photon index is 2.16+/-0.28 and 2.11+/-0.14 respectively and the absorbed (unabsorbed) flux in 2-10 keV range is 1.67E-11 (2.3E-11) ergs cm-2 s-1 and 5.12E-11 (7E-11) respectively. For a distance of 8 kpc, the unabsorbed flux during Jun 14th observation translates into a luminosity of 1.76E35 erg s-1 and during the Jun 29th observation to 5.36E35 ergs s-1.
These new observations clearly showed that the flux has increased by an order of magnitude since the last observation on May 31st. [ATel #2656].
Following re-brightening of this source as observed during our Swift observations of Jun 14th, we obtained optical observations on Jun 18th at UT = 13:33:22 using Faulkes Telescope South in R and SDSS-i' band for a total of 400s and 600 s respectively. No optical counterpart is detected within the Swift error circle. However, the calculated upper limits in R and SDSS-i' bands at 3 sigma confidence level are 20.5 and 21.4 mag respectively. The non-detections are likely caused by the high extinction.
Further Swift-XRT observations are scheduled to monitor the behavior of the source.
We thank the Swift team for making these observations possible.